Manual revision 017
Appendix II: NMEA Message Simulation Program
SBE 33
48
Appendix II:
NMEA Message Simulation Program
Sea-Bird provides a NMEA message simulation program, NMEATest, as a
troubleshooting aid. NMEATest, part of the Seasoft V2 package, simulates a
NMEA navigation devices transmitting NMEA messages. If the system does
not work with the actual NMEA navigation device, but works with
NMEATest, the problem is with the interface cable from the NMEA
navigation device to the SBE 33 or in the NMEA navigation device itself.
NMEATest is just a simulation, and does not provide an actual data stream
from an actual NMEA navigation device. The data transmission baud rate
(4800 or 9600) and time between messages are user-programmable. The
NMEA message format (RMA, RMC, GLL, or GGA) generated by the
program is also user-programmable. Alternatively, the user can specify an
existing raw NMEA data file to use for the simulation; see
Appendix I:
NMEA Navigation Device Message and Data Formats
for the required raw
data format.
To execute the simulation program, a
second computer
(computer 2) is
needed to emulate the NMEA navigation device. A laptop computer is
adequate for this purpose. Install NMEATest on computer 2 (NMEATest is
part of the SBE Data Processing installation).
Use the NMEA Interface test cable (PN 801422 - supplied with the SBE 33) to
connect
NMEA Input
on the SBE 33 to the simulation computer. The simulation
test cable connections are:
MS3106A12S-3S
DB-9S
Function
Pin A
Pin 3
NMEA
A
(signal)
Pin B
Pin 5
NMEA
B
(signal return)
Proceed as follows (instructions are written assuming you are using a second
computer to emulate the NMEA navigation device):
1.
On computer 1, set up Seaterm to communicate with the SBE 33 at 9600
or 19200 baud, 7 or 8 data bits, no or even parity (Steps 1 and 2 in
Setting
Up and Testing System
in
Section 3: Setting Up System
).
2.
Turn on power to the SBE 33. The SBE 33 status message displays in
Seaterm:
SBE 33/36 Deck Unit V3.0 setup:
PC baud rate = 9600
CTD baud rate = 4800
8 data bits, no parity
NMEA baud rate = 4800
NMEA messages decoded =
GGA, GLL, RMA, RMC, TRF, DBT, DPT
Surface PAR disabled
NMEA depth disabled
start mode = echo characters to and from the instrument
Press @ to change the 33/36 Deck Unit setup
3.
Type
@
to access the NMEA Interface menu.
4.
Type
3
and press the Enter key to switch to mode 3.
Note:
The SBE 33 must be connected to the
Water Sampler to test the NMEA
interface. If it is not connected, noise
on the open
Sea Cable
connector will
interfere with communication with the
SBE 33.
Note:
You can also run the simulation
using only one computer
, if the
computer has a spare COM port.
Note:
While NMEATest can
generate
messages in only the four formats
shown, it can
run
using an existing
raw NMEA data file in these formats
as well as TRF, DBT, and DPT.
